Changing the shape and color of hair is an important field of modern cosmetics. Consumers turn to color-changing agents for the fashionable coloring of hairstyles or to cover grey or even white hair with fashionable or natural color shades.
In order to provide color-changing cosmetic agents, in particular for the skin or keratin-containing fibers, such as human hair, a person skilled in the art is aware of various systems depending on the requirements of the coloration or color change.
What are known as oxidation dyes are used for permanent intense dyes having appropriate fastness properties. Such dyes usually include oxidation dye precursor products, or what are known as developer components and coupler components. The developer components form the actual dyes under the influence of oxidizing agents with coupling to one or more coupler components. The oxidation dyes are characterized by intense, excellent, long-lasting color results.
During the oxidative color change process, developers and couplers diffuse separately into the keratin fibers and form the actual dyes in a chemical reaction with one another under the influence of ammonia as alkalizing agent (or other alkalizing agents such as monoethanolamine) and an oxidizing agent (usually hydrogen peroxide). The developers known from the prior art usually do not form any dyes with one another, or form only very weak, non-specific dyes, and require one or more couplers in order to produce an intense color nuance. The couplers known from the prior art also form only weak dyes with one another and must be made to react with at least one developer in order to attain an intense, bright color result.
In spite of their advantageous coloring properties, oxidative hair dyes are associated with various disadvantages for the user. In particular, it is suspected for some of the conventional oxidation dye precursor products, including p-phenylenediamine itself, that these have an irritating or aggravating effect for some users and thus trigger sensitizations or even allergic reactions. For these substances, there is thus a need for further improvement in respect of their physiological compatibility profile. Many compounds have been researched in the quest for replacement substances, however these are often afflicted by use-related problems, such as insufficient fastness properties. In addition, in spite of already highly developed dyeing systems, there is also a need for dyeing systems with which excellent brightness and intensity of the dyeing results can be attained and which at the same time have very good durability and excellent homogeneity.
It is therefore desirable to reduce the above-mentioned disadvantages of oxidative hair dyes. Dyes should produce intense colorings with high colorfulness and with good resistance to external influences, in particular with good fastness to light and washing, which also do not experience any color fading or color change, even once the hair has been shampooed multiple times. In addition, the dyes should have excellent leveling capacity to the greatest possible extent and should be less selective, i.e. they should result in uniform, consistent color results to the greatest possible extent on hair that has been pre-treated to varying degrees. In addition, the dyes should have an advantageous profile in terms of toxicology.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with this background of the invention.